Controllable Fabrication of Au-Coated AFM Probes via a Wet-Chemistry Procedure

Tip-enhanced Raman spectroscopy (TERS), which offers a spatial resolution far beyond the limitations of the optical diffraction and detection sensitivity down to a single molecular level, has become one of the powerful techniques applied in current nanoscience and technology. However, the excellent performance of a TERS system is very much dependent on the quality of metallized probes used in TERS characterization. Thus, how to prepare higher-quality probes plays a vital role in the development and application of TERS technique. In this work, one simple wet-chemistry procedure was designed to fabricate atomic force microscopy-based TERS (AFM-TERS) probes. Through the controlled growth of a gold film on a commercial silicon AFM probe, TERS probes with different apex diameters were prepared successfully. A series of TERS results indicated that the probes with the apex size of 50~60 nm had the maximum TERS enhancement, and the Raman enhancement factor was in the range of 10(6) to 10(7). Compared with those prepared by other fabrication methods, our TERS probes fabricated by this wet-chemistry method have the virtues of good stability, high reproducibility, and strong enhancement effect.